A new method allowed researchers to estimate the magnetic field of a distant exoplanet and calculate its momentum.
The finding marks the first time researches have been able to determine these factors and shape the magnetosphere of a planet orbiting a far-off star, Lomonosov Moscow State University reported.
The planet, dubbed HD 209458b (Osiris), is a hot Jupiter about one-third larger and lighter than the Red Planet. It orbits extremely closely to its host star HD 209458, making one revolution around its star every 3.5 Earth days.
Using observations from the Hubble Space Telescope of the HD 209458b as it moved across the Lyman-alpha line, crossing the stellar disc. They looked at the absorption of the star's radiation by the atmosphere of the nearby planet; this allowed them to estimate the shape of the gas cloud surrounding the planet, and determine the configuration of its magnetosphere.
"We modeled the formation of the cloud of hot hydrogen around the planet and showed that only one configuration, which corresponds to specific values of the magnetic moment and the parameters of the stellar wind, allowed us to reproduce the observations" said Kristina Kislyakova of the Space Research Institute of the Austrian Academy of Sciences.
To make the model as accurate as possible the researchers looked at factors that influence interaction between the stellar wind and the atmosphere of the planet such as "ionization, gravitational effects, pressure, radiation acceleration, and the spectral line broadening" of neutral atmospheric particles.
The team determine the size of the atomic hydrogen envelope was determined by interactions between gas outflows from the planet and the incoming stellar wind protons, which occur in the magnetosphere.
"The planet's magnetosphere was relatively small beeing only 2.9 planetary radii corresponding to a magnetic moment of only 10 [percent] of the magnetic moment of Jupiter," said Kislyakova.
The findings were published in a recent edition of the journal Science.
